Personal watercraft generally include a water propulsion device which is powered by an internal combustion engine. These watercraft are generally quite small in size, often limited to use by a single person.
The engine of the watercraft is positioned in an enclosed engine compartment defined by a hull of the watercraft. Due to the small size of the watercraft, the engine compartment is very small, and thus the engine is arranged in fairly compact fashion therein.
To avoid the need for a complex lubrication system, which contributes to a larger engine size and cost, in many cases lubricant is supplied to the engine along with the fuel. This is a very common arrangement for internal combustion engines operating on two-cycle principle. For example, lubricant may be pumped from an oil tank into the fuel tank for mixing with the fuel, with the combined mixture then delivered to the engine.
In some instances, the fuel is supplied to air passing through an intake system with a floatless carburetor. The floatless carburetor typically has a fuel chamber separated from an atmospheric chamber by a diaphragm. The fuel chamber is typically filled by fuel supplied through a fuel pump. The fuel is then supplied from the fuel chamber to a venturi. The venturi introduces fuel into the airstream and allows the mixing of the fuel and air within the carburetor.
A mixture of lubricant and fuel can be delivered with such a carburetor. A problem with this arrangement, however, is that it is difficult to control the rate at which lubricant is delivered to the engine at a given time since it is mixed with a large quantity of fuel. At the same time, attempts to provide lubricant in other manners must not interfere with the operation of the carburetor's main function, that of delivering fuel.
Accordingly, it is desired to have a lubrication system wherein the lubricant flow rate to the engine can be more accurately controlled based on engine conditions. It is also desired for such a lubrication system where the lubricant is introduced into the fuel stream and mixed with the fuel being supplied by a floatless carburetor, while at the same time ensuring that the lubricant delivery does not interrupt the proper operation of the carburetor.